Au-Sn-Bi ALLOY POWDER PASTE, Au-Sn-Bi ALLOY THIN FILM, AND METHOD FOR FORMING Au-Sn-Bi ALLOY THIN FILM

Abstract

The present invention provides to an Au—Sn—Bi alloy film which has an excellent bondability on a metalized layer formed on an LED element or a substrate as a bonding layer made of the Au—Sn—Bi alloy and is uniform and thin. In the present invention, an Au—Sn—Bi alloy thin film which has the thickness of 5 μm or less and includes at least a eutectic structure can be formed by using an Au—Sn—Bi alloy powder paste that mixes the Au—Sn alloy powder containing 20 wt % to 25 wt % of Sn, 0.1 wt % to 5.0 wt % of Bi, and a balance of Au, and having a particle diameter of 10 μm or less with an RA flux of 15 wt % to 30 wt %, screen printing the Au—Sn—Bi alloy powder paste in a predetermined region on the Au metallized layer, and subsequently, heating, melting and then solidifying the Au—Sn—Bi alloy powder.

1 . An Au—Sn—Bi alloy powder paste which is a mixture comprising: an Au—Sn—Bi alloy powder containing 20 wt % to 25 wt % of Sn, 0.1 wt % to 5.0 wt % of Bi, and the balance of Au and having a particle diameter of 10 μm or less; and 15 wt % to 30 wt % of an flux containing at least an activator. 
     
     
         2 . An Au—Sn—Bi alloy thin film comprising: 20 wt % to 25 wt % of Sn, 0.1 wt % to 5.0 wt % of Bi, and the balance of Au, and having a thickness of 5 μm or less, the thin film having:
 at least a eutectic structure. 
 
     
     
         3 . A method for forming an Au—Sn—Bi alloy, comprising:
 screen-printing an Au—Sn—Bi alloy powder paste in a predetermined region on a metallized layer, the paste being a mixture comprising: an Au—Sn—Bi alloy powder containing 20 wt % to 25 wt % of Sn, 0.1 wt % to 5.0 wt % of Bi, and the balance of Au and having a particle diameter of 10 μm or less; and 15 wt % to 30 wt % of an flux containing at least an activator; and 
 heating, melting and then solidifying the Au—Sn—Bi alloy powder to form an Au—Sn alloy thin film having at least a eutectic structure. 
 
     
     
         4 . The method for forming an Au—Sn alloy thin film according to  claim 3 ,
 wherein the screen-printing is performed by gap printing using a screen mask which has a mesh corresponding to the predetermined region.